Texas Bureau of Economic Geology Guide to the Permian Reef Geology Trail, McKittrick Canyon, Guadalupe Mountains National Park, Texas

Cover

Introduction
Don G. Bebout, Charles Kerans, and Paul M. Harris

Geologic Setting
The Trail

Toe of Slope
Alton Brown and Robert G. Loucks

Stop 1. Quaternary-Age Alluvial Conglomerate
Stop 2. Distal Toe-of-Slope Wackestone
Stop 3. Distal Toe-of-Slope Debris-Flow Deposits
Stop 4. Vertical and Lateral Changes in Toe-of-Slope Sedimentation
Stop 5. Stratigraphic Relations on the South Side of the Canyon
Stop 6. Turbidites and Debris-Flow Deposits
Stop 7. Transition from Toe of Slope to Slope
Stop 8. Top of Lamar Limestone Member
Summary

Slope
Denise Mruk and Don G. Bebout

Stop 9. Mud-Dominated Gravity-Flow Deposits
Stop 10. Slope/Toe-of-Slope Burrowed Wackestone
Stop 11. Grain-Dominated Gravity-Flow Deposits
Stop 12. Slope Mud-Rich Carbonate
Stop 13. Slope Mixed Siliciclastics and Carbonates
Stop 14. Fusulinid-Rich, Shelf-Margin Talus
Summary

Reef
Brenda L. Kirkland, Susan A. Longacre, and Emily L. Stoudt

Stop 15. Interbedded Basal Reef and Slope Deposits
Stop 16. Well-Exposed Sponge Archaeolithoporella Boundstone
Stop 17. Tubiphytes/Acanthocladia Boundstone
Stop 18. Fusulinids within the Reef
Stop 19. Pockets or Neptunian Dikes within the Reef
Stop 20. Typical Reef Outcrops and Cave Fill
Stop 21. Reef Diagenesis
Stop 22. Upper Reef—Collenella, Fusulinids, and Dolomite
Summary

Outer Shelf and Shelf Crest
Charles Kerans and Paul M. Harris

Stop 23. Reef/Outer-Shelf Transition Zone
Stop 24. Exposure Surface within Yates Outer Shelf
Stop 25. Outer-Shelf Packstone-Grainstone Cycles
Stop 26. Mixed Siliciclastic/Carbonate Outer-Shelf Cycles
Stop 27. Shelf-Crest Cycles
Stop 28. Outer-Shelf Dolopackstones
Summary

Geology Loop Trail
Alton Brown and Robert G. Loucks

Stop 29. Margin of Slope Gully
Stop 30. Slope Gully Fill

Acknowledgments

References

(click on image for an enlargement in a new window)

1. Map of the Capitan reef front, Guadalupe Mountains, and location of McKittrick Canyon, other major canyons along the escarpment, Guadalupe Peak, and El Capitan

2. Topographic map of the mouth of McKittrick Canyon showing the location of the Permian Reef Geology Trail and trail stops

3. Map of the Permian Basin showing the location of the upper Guadalupian reef trend, oil and gas fields producing from equivalent strata in the subsurface, and mountains with exposures of upper Guadalupian formations

4. Cross section showing shelf-to-basin correlations of the Capitan Formation and equivalents

5. Hypothetical paleobathymetric profiles across the Capitan shelf margin

6. Photomosaic of the north wall of McKittrick Canyon showing formation boundaries, interpreted depositional facies profiles, and correlation horizons within the Seven Rivers and Yates Formations

7. Diagrammatic sketch of the north wall of McKittrick Canyon showing the stratigraphy, depositional environments, present-day erosional profile, and general location of the Permian Reef Geology Trail

8. Dip-oriented, structural cross section of the toe-of-slope Lamar Limestone Member exposed on the north wall at the mouth of McKittrick Canyon

9. Stop 2, trail and thin-section photographs

10. Stop 3, trail and thin-section photographs

11. Stop 3, measured section with interpreted depositional processes

12. Stop 4, trail and thin-section photographs

13. Regional variations along a reef-to-basin cross section of depositional dip and lithology and thickness of the Lamar Limestone Member

14. Stratigraphic section of the interval near the peloidal packstone along the north wall of McKittrick Canyon

15. Interpretation of lithology and bedding relationships on the cliff of Lamar Limestone Member on the south side of McKittrick Canyon (Stop 5)

16. Photograph of the south wall of McKittrick Canyon across from Stop 5 showing the basinal carbonate members merging with the Capitan Limestone

17. Photograph of ungraded skeletal packstone along the trail at Stop 6

18. Stop 7, trail and thin-section photographs

19. Measured section at Stop 7 with depositional interpretations

20. Dip-oriented oblique aerial photograph and an interpretive tracing of the slope and toe-of-slope portion of the Permian Reef Geology Trail

21. Stop 9, trail and thin-section photographs

22. Measured section (perpendicular to dip) of grain-dominated gravity-flow deposits, Stop 11

23. Stop 11, trail photographs of the grain-dominated gravity-flow deposits

24. Diagrammatic sketch of the slope beds of Stops 12-14 showing carbonate textures and fabrics encountered along this part of the trail and location of stops relative to elevation markers and geographic features

25. Stop 13, trail and thin-section photographs

26. Stop 14, trail and thin-section photographs

27. Stop 15, basal reef

28. Stop 16, sponges of the Capitan reef

29. Stop 17, Tubiphytes and Acanthocladia in reef

30. Stop 18, fusulinids in reef, and Stop 19, pockets or neptunian dikes

31. Stop 20, Permian internal sediment and cave fill in reef

32. Stop 21, reef cement

33. Stop 21, reef cement, and Stop 22, Collenella zone

34. Oblique aerial photograph of upper portion of Permian Reef Geology Trail showing reef Stops 17-22 and shelf Stops 23-28, elevation markers, major switchbacks, and key stratigraphic relations

35. Measured sections for the outer shelf and shelf crest portion of the trail showing stratigraphic nomenclature, sequences and cycles, and the position of Stops 23-28

36. Outcrop and thin-section photographs of Stop 23 reef/outer shelf transition

37. Schematic diagram showing facies relations documenting exposure of outer shelf associated with top Yates 4 sequence boundary

38. Outcrop and thin-section photographs of Stop 24 exposure surface

39. Approximate time line connecting youngest known occurrence of the fusulinid Polydiexodina along the trail

40. Panoramic photomosaic and interpretive sketch of the portion of the trail discussed in Stop 25 looking down the trail into the basin

41. Cross section of outer shelf strata in Yates 4, Yates—Tansill 1 sequences from the area of Stop 25

42. Outcrop and thin-section photographs of Stop 25 outer-shelf cycle

43. Schematic facies patterns seen in outer shelf fall-in beds of Stop 25

44. Outcrop and thin-section photographs of Stops 26-28 siliciclastic-carbonate and carbonate cycles

45. Trail photograph of margin of slope gully at Stop 29

46. Schematic strike cross section between the lower Grotto (Stop 4) and Stop 30